A proposal for research on a wide variety of specific problems on the male and female reproductive tract. Among the investigations on spermatozoa will be isolation and chemical analysis of the fibrous sheath and freeze cleaving studies on the changes in membrane structure associated with capacitation, activation and the acrosome reaction. An effort will be made to localize and quantitate tubulin in the dissociated cell types of the seminiferous tubules. The ultrastructure of the epididymal epithelium from different segments of the duct will be studied and correlated with the androgen-binding capacity of its cytosol in normal rats and after efferent duct ligation. Work on the female reproductive tract will include explorations of the significance of nexuses between granulosa cells of developing follicles and studies on the development of cell junctions during decidualization. In addition, there will be an ultrastructural study of testicular biopsies from infertile men and exploration of the value of scanning microscopy for clinical evaluation of human semen.